Methods for the production of hydrogen

ABSTRACT

Methods, processes, and apparatuses for the production of hydrogen gases are provided. A catalytic amount of iodine is dissolved in a hydrocarbon fuel source, such as cyclopropane and/or benzene, and the mixture is heated to a temperature greater than about 80° C. A reaction vessel capable of maintaining pressures greater than 1 atmosphere is used. The hydrogen gas thus produced is recovered, and optionally purified.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from U.S. ProvisionalApplication No. 60/414,462, filed Sep. 26, 2002, and U.S. ProvisionalApplication No. 60/443,246, filed Jan. 28, 2003, and which applicationsare incorporated herein by reference in their entireties.

FIELD OF INVENTION

[0002] The present invention relates to the production of hydrogen gas.

BACKGROUND

[0003] Hydrogen gas is used in the manufacture of many productsincluding metals, hydrotreating and hydrocracking in refineries,commercial catalytic hydrogenation for high volume chemicals, ediblefats and oils processing, and in semiconductors and microelectronicsindustrial processes. Hydrogen gas is also an important fuel source formany energy conversion devices. For example, fuel cells use purifiedhydrogen and an oxidant to produce an electrical potential. Thus,hydrogen gas is a critical component for the production of high-gradechemicals and clean-burning fuels, and is the cleanest, highest energycontent fuel on a weight basis. However, because hydrogen is a veryexplosive gas, its use has been limited by the need for supplying it inhigh-pressure cylinders.

[0004] There are numerous industrial methods for the generation ofhydrogen gas including electrolysis of water (U.S. Pat. No. 5,037,518),reaction of a metal with an acid, reaction of certain metals with astrongly alkaline compound, reaction of calcium hydride with water (U.S.Pat. No. 5,833,934), steam reforming of methyl alcohol or methane innatural gas (U.S. Pat. Nos. 4,454,207 and 4,642,272), releasing ofhydrogen gas from a hydrogen-loaded hydrogen-absorbing metal or alloy(U.S. Pat. No. 6,596,055), and so on.

[0005] One of the current limitations in developing fuel cell technologyis the lack of an efficient, controllable, and cost-effective method forproducing hydrogen (H₂) on an ‘as-needed’ basis for reaction in the fuelcell. For example, current chemical hydride methods of generating H₂have the drawback that once H₂ production begins, the reaction cannot bestopped. Thus, H₂ continues to be produced and either must be used bythe fuel cell, stored as a gas, or wasted due to release. Alternatively,H₂ for a fuel cell can be stored as liquid hydrogen. However, thisrequires specialized equipment to safely store the liquid H₂ under thenecessary temperature and pressure conditions. Additional shortcomingsof current methods include low yield from the hydrogen producingreactions, severe processing conditions such as high reactiontemperatures, consumption of a large quantity of energy, and highoperating costs. Thus, efficient and cost-effective methods forproducing H₂ on demand are needed, preferably where hydrogen is producedfrom a hydrocarbon fuel source.

[0006] Hydrogen has been generated from hydrocarbon fuel sources in aprocess called steam reforming where steam and a hydrocarbon are reactedin the presence of a catalyst. Examples of suitable hydrocarbons arealcohols, such as methanol or ethanol, and alkanes such as methane,propane, gasoline or kerosene. Steam reforming requires an elevatedoperating temperature of between 250° C. and 900° C., and producesprimarily hydrogen and carbon dioxide, with lesser quantities of carbonmonoxide also being formed. Efficient operation of the fuel processorrequires careful indexing and control of the ratio of water (steam) tocarbon-containing feedstock. Trace quantities of unreacted reactants andtrace quantities of byproducts also can result from steam reforming.Therefore, a subsequent purification process to remove the impurities isnormally employed. The process thus requires high capital costs. Inaddition, due to the size of the reactor, steam reforming is notsuitable for the purpose of hydrogen supply to fuel cells which mustnaturally be very compact in size and light in weight. Thus, steamreforming is only economically viable for large, commercial scaleproduction of hydrogen gas.

[0007] Thus, there is a need for methods of producing of hydrogen gasthat are efficient and cost-effective. Preferably the methods allow forthe production of hydrogen on an as-needed basis with little or noimpurities being formed, requires low capital costs, and produceshydrogen gas in a process that is environmentally friendly.

SUMMARY

[0008] The present invention provides methods, apparatuses, andprocesses for the production of hydrogen gas by reacting iodine (I₂)with either benzene or cyclohexane in the liquid phase. The reactionproduces H₂ and a solid residue composed primarily of carbon (C). Thereaction can be initiated by changing the pressure and/or temperature ofthe reactants, and the reaction can be selectively and repeatedlystarted and stopped by adjusting the temperature and/or pressure.Additionally, the ratio of the catalyst to the hydrocarbon fuel can bevaried to influence the rate of hydrogen production.

[0009] In one aspect, the invention provides method for generation ofhydrogen gas, the method comprising contacting a hydrocarbon fuel withiodine to provide a mixture and heating the mixture under pressurethereby generating hydrogen gas. The hydrocarbon fuel can be acycloalkane, such as cyclohexane or an aryl compound, such as benzene.In addition, mixtures of cycloalkane and aryl compounds can be used asthe hydrocarbon fuel. Preferably, catalytic amounts of iodine are used.The mixture can be heated in a reaction vessel to a temperature of about60° C. to 500° C., preferably about 80° C. to about 250° C., morepreferably about 80° C. to 100° C. The pressure is preferably greaterthan about 2 atmospheres. The hydrogen gas thus produced can becollected and purified.

[0010] In another aspect, the invention provides systems for theproduction of hydrogen gas. The systems comprise a reaction containercontaining a composition comprising a hydrocarbon fuel and iodine, andcausing the composition to react in the container to generate hydrogengas. The hydrocarbon fuel can be a cycloalkane, such as cyclohexane, anaryl compound, such as benzene or mixtures of cycloalkane and arylcompounds. Preferably, catalytic amounts of iodine are used. The mixturecan be heated in a reaction vessel to a temperature of about 60° C. to500° C., preferably about 80° C. to about 250° C., more preferably aboveabout 80° C. The hydrogen gas thus produced can be collected andpurified.

[0011] These and other aspects of the present invention will becomeevident upon reference to the following detailed description. Inaddition, various references are set forth herein which describe in moredetail certain procedures or compositions, and are thereforeincorporated by reference in their entirety.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 illustrates an apparatus for use in the present invention.

[0013]FIG. 2 depicts a plot of output data from a mass spectrometerdemonstrating levels of H₂ detected exiting a reaction vessel as thereaction temperature is varied.

DETAILED DESCRIPTION

[0014] I. Definitions

[0015] Unless otherwise stated, the following terms used in thisapplication, including the specification and claims, have thedefinitions given below. It must be noted that, as used in thespecification and the appended claims, the singular forms “a,” “an” and“the” include plural referents unless the context clearly dictatesotherwise. Definition of standard chemistry terms may be found inreference works, including Carey and Sundberg (1992) “Advanced OrganicChemistry 3^(rd) Ed.” Vols. A and B, Plenum Press, New York, and Cottonet al. (1999) “Advanced Inorganic Chemistry 6^(th) Ed.” Wiley, New York.

[0016] The term “cycloalkyl” means the monovalent branched or unbranchedsaturated cyclic hydrocarbon compound, consisting solely of carbon andhydrogen atoms, having from three to twelve carbon atoms inclusive,unless otherwise indicated. Examples of cyclolkyl compounds include, butare not limited to, cyclopropane, cyclopentane, cyclohexane,cycloheptane, and the like.

[0017] The term “aryl” means the monovalent monocyclic aromatichydrocarbon radical consisting of one or more fused rings in which atleast one ring is aromatic in nature, which can optionally besubstituted with hydroxy, cyano, lower alkyl, lower alkoxy, thioalkyl,halogen, haloalkyl, hydroxyalkyl, nitro, alkoxycarbonyl, amino,alkylamino, dialkylamino, aminocarbonyl, carbonylamino, aminosulfonyl,sulfonylamino, and/or trifluoromethyl, unless otherwise indicated.Examples of aryl radicals include, but are not limited to, phenyl,naphthyl, biphenyl, indanyl, anthraquinolyl, and the like.

[0018] The term “halogen” as used herein refers to fluorine, bromine,chlorine and/or iodine.

[0019] II. Modes of Carrying Out the Invention

[0020] The present invention discloses methods, apparatus, and processesfor the production of hydrogen gas. The methods and processes disclosedherein are advantageous in that they provide hydrogen gas that is freeof carbon dioxide, carbon monoxide, sulfur, nitrogen and steam. Further,hydrogen production can be initiated when needed by either raising thetemperature to about 60° C. to 500° C., or by increasing the reactionpressure to above atmospheric pressure. Further, the production ofhydrogen can be terminated by lowering the temperature below about 70°C., or by decreasing the reaction pressure to about atmosphericpressure.

[0021] The methods of the invention utilize compositions of hydrocarbonfuel sources mixed with iodine. In the methods of producing hydrogen,the compositions are heated to a temperature of about 60° C. to 500° C.,while the pressure in the reaction vessel is allowed to increase toabove one atmosphere. Alternatively, the composition is first heated toa temperature of about 60° C. to 500° C., and subsequently the pressurein the reaction vessel is allowed to increase to above one atmosphere.In yet another aspect, the composition is first pressurized to above oneatmosphere, and then the temperature is raised to about 60° C. to 500°C. The hydrogen produced can be used immediately, purified, or collectedand stored for later use.

[0022] The composition for use in the inventive methods include ahydrocarbon fuel sources and a catalyst. The hydrocarbon fuel source canbe a cycloalkyl compound, an aryl compound, or mixtures thereof.Preferably, the cycloalkyl compound is cyclohexane, the aryl compound isbenzene, and the catalyst is iodine. Without being bound by anyparticular theory, it is believed that hydrogen gas is producedaccording to the following reaction scheme:

C₆H₁₂+6*I₂<=>C_((S))+12*HI<=>C_((S))+6*H₂ +6*I ₂  (1)

C₆H₆+3*I₂<=>C_((S))+6*HI<=>C_((S))+3*H₂ +3*I ₂  (2)

[0023] Thus, I₂ serves as a catalyst and is not consumed by thereaction. It is believed that the presence of deprotonated benzene orcyclohexane is involved in the conversion of HI to H₂ and I₂. Therefore,in one aspect of the invention, the composition for use in the methodsof the invention comprise hydrocarbon fuel and the catalyt in a ratio ofabout 200:1 to about 1:2 (mol/mol), preferably about 100:1 to about 5:1,or more preferably about 50:1 to about 10:1, or any ratio in between.

[0024] Typically, the hydrocarbon fuels and the catalyst are mixed inthe desired ratio. The components of the composition can be added to theraction chamber separately and then mixed, or they can be first mixedand then added to the reaction chamber.

[0025] In the methods of the invention, the hydrocarbon and the iodinecatalyst are caused to be reacted thereby producing hydrogen. In oneaspect, the production of hydrogen can be initated by increasing thetemperature of the reactants to a temperature that is above the ambienttemperature. The temperature can be increased to about 60° C. to about800° C., more preferably from about 80° C. to about 250° C., even morepreferably to a temperature of about 80° C. to 100° C. Thus, when thecatalyst is iodine (mp=113° C.), the temperature is preferably aboveabout 80° C.

[0026] The temperature can be increased by any one of the known methods.Such methods include direct heat, such as from a furnance or a bunsenburner, electrical resistive heating, thermal resistive heating,microwave heating, infrared heating, and heating using laser beam, radiofrequency, or ultrasonic irradiation, and the like.

[0027] In another aspect of the invention, the production of hydrogencan be initiated by increasing the pressure of the reactants to apressure that is above atmospheric pressure. The pressure can beincreased to about 1.5 atmospheres to about 400 atmospheres, morepreferably about 2 atmospheres to about 200 atmosphere, even morepreferably about 2 atmospheres to about 2.5 atmospheres. The pressurecan be increased using any one of the known methods. Such methodsinclude, for example, heating the compositions in a reaction chamberhaving a fixed volume, introducing inert gases, such as helium, neon,argon, kryptonite, and xenon, or non-reactant gases into the reactionchamber thereby increasing the pressure, and the like.

[0028] Typically, the composition can be heated to a temperature ofabout 80° C. to about 100° C., and the pressure can be allowed toincrease to between about 2 atmospheres to about 2.5 atmospheres. Thepressure can be maintained between about 2 atmospheres to about 2.5atmospheres by venting the gases from the reaction vessel, eitherperiodically or in a continuous controlled manner. As one of skill inthe art will recognize, the gases vented can be a mixture of thehydrocarbon fuel, hydrogen, atmospheric gases, iodine and HI. Thus, thehydrogen gas produced may need to be purified. Further, the hydrocarbonsthat are vented can be reclaimed and added back to the reaction chamberif desired.

[0029] The completion of the reaction yields carbon deposits in additionto hydrogen gas. The carbon deposits can ignite upon contact with airthereby generating CO and CO₂. Therefore, precautions to guard againstuncontrolled ignition of the carbon byproduct may be required. Forexample, the reaction can be carried out under an inert atmosphere suchas a nitrogen, an argon or a helium atmosphere; the reaction can becarried out under normal atmosphere and an inert gas, such as nitrogen,argon or helium, can be injected into the reaction chamber as thehydrogen producing reaction approaches completion; additionalhydrocarbon or an inert liquid can be added to the reaction chamber asthe hydrogen producing reaction approached completion; or the reactioncan be stopped before completion so that the carbon deposits remaincovered with a liquid instead of being exposed to air.

[0030] As can be seen from the reaction scheme above, each mole ofliquid cyclohexane reacts to form 6 moles of molecular hydrogen.Similarly, each mole of liquid benzene reacts to form 3 moles ofmolecular hydrogen. As a result, the reaction is capable of producingsubstantial pressure increases when carried out in a fixed volume. Forexample, a 100 ml test tube reaction vessel containing 0.093 moles (10ml) of cyclohexane and 0.5 g of I₂ is calculated to have a pressure ofabout 2.5 atmospheres prior to initiation of the reaction at about 110°C. The pressue is due to the vapor pressue of cyclohexane. However, uponcomplete reaction, about 0.56 moles of H₂ will be produced. According tothe ideal gas law, the completion of reaction will produce a pressure ofabout 170 atmospheres at 110° C. Thus, the conversion of cyclohexane tocarbon and hydrogen gas under ideal conditions results in a roughly70-fold pressure increase within the reaction vessel.

[0031] As discussed above, the I₂ acts as a catalyst which is normallynot consumed during the reaction. In another aspect, the reaction can beallowed to proceed until it terminates due to either exhaustion of thehydrocarbon reagent or the inability to maintain the necessary pressurein the reaction vessel when insufficient hydrocarbon remains. Thereaction can then restarted by adding additional hydrocarbon alone tothe reaction vessel. This process of allowing the reaction to exhaustitself and then adding additional hydrocarbon can be repeated for manycycles. However, it was found that at the end of the 10 cycles, roughly90% of the I₂ still remained in the reaction vessel. Although I₂ is notconsumed by the reaction, the amount of I₂ available is believed to beimportant, as the rate of hydrogen production may be controlled byvarying the amount of I₂ present in the reaction vessel. The rate ofhydrogen production can be increased by increasing the concentration ofiodine in the reaction composition. Further, it was found thatincreasing the concentration of iodine within the composition results inhaving to increase the temperature of the composition in order toinitiate the production of hydrogen. Thus, increasing the concentrationof iodine in the reaction composition requires that the temperature beraised to above about 80° C. to initiate hydrogen gas production.

[0032] This apparent catalytic behavior of I₂ when using benzene orcyclohexane as the reagent is in contrast to the behavior when thereagent is a multi-ring aromatic, such as naphthalene or anthracene. Incomparative examples involving similar reaction conditions except forthe use of naphthalene or anthracene as the hydrocarbon, the reactionresulted in a) incomplete consumption of the hydrocarbon, b) anoticeable amount of I₂ consumption during the course of the reaction,and c) production of HI as a byproduct of the reaction. The hydrogenproduction for these experiments was not characterized.

[0033] In one experiment, the methods described above were carried out,except the composition contained the aliphatic hydrocarbon isooctane asthe fuel source. In this experiment, no reaction was observed after thesolution was heated to temperatures as high as 220° C.

[0034] The hydrogen gas product can be purified, stored for later use,or delivered for use in processes requiring hydrogen gas. For example,the hydrogen gas product can be purified by passing through a filterthat selectively allows the product gas to pass through, while thepotential impurities, such carbon and HI, are excluded.

[0035] The hydrogen gas product, either directly from the reactionchamber or purified, can be stored in a suitable storage device, such asa hydride bed or storage tank, or delivered for use in processesrequiring purified hydrogen gas. For example, the hydrogen gas productcan be delivered to a fuel cell stack. Fuel cell stack includes at leastone fuel cell, and typically includes multiple fuel cells coupledtogether. The fuel cell stack receives hydrogen gas from the reactionchamber and produces an electric current therefrom as the hydrogen gasis reacted with oxygen to form water. The electric current produced bythe fuel cell stack can then be used to meet the electric load appliedby one or more associated devices, such as vehicles, households,generators, boats, and the like. Examples of suitable fuel cells includeproton exchange membrane (PEM) fuel cells and alkaline fuel cells.

EXAMPLES

[0036] Below are examples of specific embodiments for carrying out thepresent invention. The examples are offered for illustrative purposesonly, and are not intended to limit the scope of the present inventionin any way. Efforts have been made to ensure accuracy with respect tonumbers used (e.g., amounts, temperatures, etc.), but some experimentalerror and deviation should, of course, be allowed for.

Example 1

[0037] Production of Hydrogen Gas From Cyclohexane

[0038] A 100 mL test tube, having thick walls capable of withstandingincreased pressures and having Teflon screwcaps with inlets, was used asa reaction vessel (FIG. 1). Into the reaction vessel was placed 0.5 g(0.002 mol) of solid I₂ and 10 mL (0.09 mol) of cyclohexane(density=0.77 g/ml). The catalyst and the hydrocarbon thus have aninitial molar ratio of roughly 1:45. The test tube was tightly screwed,as shown in FIG. 1, and then heated to about 80° C., thereby increasingthe pressure within the reaction vessel. The temperature was maintainedbetween 80° C. and 100° C., and the pressure was maintained between 2and 2.5 atmospheres by periodically venting the gases. The hydrogenproduced was collected by opening the valve 145. Thus, hydrogen gas canbe produced by the reaction of cyclohexane with I₂.

Example 2

[0039] Production of Hydrogen Gas From Benzene

[0040] The procedure of Example 1 was used, except approximately 10 mL(0.11 mol) of benzene (density=0.87 g/ml) was used instead ofcyclohexane. Upon heating to about 80° C., the hydrocarbon reagentwithin the reaction was consumed at a rate of approximately 1 mL/min.This very roughly corresponds to consumption of 0.1 moles/min of thehydrocarbon reagent. The reaction produced hydrogen gas and a solidcarbon residue. Raman spectrum of the carbon residue indicated that thecarbon was almost completely graphitic, with effectively no hydrogencontent. Thus, hydrogen gas can be produced by the reaction of benzenewith I₂.

Example 3

[0041] Effect of Temperature on the Production of Hydrogen Gas

[0042] The procedure of Example 2 was carried out, except thetemperature was raised to about 75° C. and maintained at thattemperature, and the pressure was maintained at between 2 and 2.5atmospheres. The production of hydrogen or the solid carbon residue wasnot observed after several hours.

[0043] The production of hydrogen gas was initiated by raising thetemperature to about 80° C., while maintaining the pressure at between 2and 2.5 atmospheres. After a time period, the reaction vessel wasallowed to cool to a temperature below about 80° C. FIG. 2 illustratesthe effect of temperature on hydrogen gas production. As can be seen inthe graph of FIG. 2, high levels of hydrogen gas were measured by massspectroscopy when the reaction temperature was above about 80° C., andlow levels of hydrogen gas were measured by mass spectroscopy when thereaction temperature was below about 80° C. The low levels of H₂registered by the mass spectrometer probably represents residual H₂ fromperiods when the reaction was active, and that this signal wouldeventually go to zero. The hydrogen producing reaction was reactivatedby raising the temperature above about 80° C. Thus, the reaction leadingto the production of H₂ can be selectively and controllably turned onand off by allowing the temperature to rise and fall in the vicinity ofthe initiation temperature.

Example 4

[0044] Production of Hydrogen Gas Using Hydrocarbon Mixtures

[0045] The procedure of Example 1 was carried out, except thehydrocarbon reagent was composed of roughly equal parts by volume ofcyclohexane and toluene. The temperature was raised to about 110° C. andmaintained at that temperature. The production of hydrogen or the solidcarbon residue was not observed. The temperature in the reaction vesselwas then increased to about 200° C., and the production of hydrogen wasdetected. Due to the higher temperature required to initiate thereaction, it is believed that the pressure within the reaction vesselwas also higher. Similarly, when cyclohexane or benzene was diluted withisooctane, higher temperatures and pressures were required to initiatethe reaction, and it is believed that the rate of hydrogen production isreduced when the benzene or cyclohexane is diluted with anotherhydrocarbon.

[0046] While the invention has been particularly shown and describedwith reference to a preferred embodiment and various alternateembodiments, it will be understood by persons skilled in the relevantart that various changes in form and details can be made therein withoutdeparting from the spirit and scope of the invention. All printedpatents and publications referred to in this application are herebyincorporated herein in their entirety by this reference.

We claim:
 1. A method for generation of hydrogen gas, the methodcomprising: contacting a hydrocarbon fuel with iodine to provide amixture thereof; and heating the mixture thereby generating hydrogengas.
 2. The method of claim 1, wherein the hydrocarbon fuel is acycloalkane or an aryl compound, or mixtures thereof.
 3. The method ofclaim 2, wherein the hydrocarbon is a cycloalkane compound.
 4. Themethod of claim 3, wherein the cycloalkane is cyclohexane.
 5. The methodof claim 2, wherein the hydrocarbon is an aryl compound.
 6. The methodof claim 5, wherein aryl compound is benzene.
 7. The method of claim 2,wherein the hydrocarbon is a mixture of a cyclohexane and an arylcompound selected from the group consisting of benzene and toluene. 8.The method of claim 1, wherein the hydrocarbon fuel and iodine are in aratio of about 1:0.001 to about 1:2 moles/moles.
 9. The method of claim8, wherein the ratio is about 1:0.01 to about 1:0.25 moles/moles. 10.The method of claim 1, wherein the mixture is heated to a temperature ofabout 60° C. to about 500° C.
 11. The method of claim 10, wherein themixture is heated to a temperature greater than about 80° C. to about100° C.
 12. The method of claim 10, wherein the mixture is heated to atemperature greater than about 80° C.
 13. The method of claim 1, furthercomprising exposing providing the mixture to increased pressure.
 14. Themethod of claim 13 wherein the pressure is greater than about 1atmosphere, and less than about 250 atmospheres.
 15. The method of claim14, wherein the pressure is greater than about 2 atmospheres.
 16. Amethod comprising the steps of: providing in a reaction container acomposition comprising a hydrocarbon fuel and iodine; and causing thecomposition to react in the container to generate hydrogen gas.
 17. Themethod of claim 16, further comprising recovering the hydrogen gas. 18.The method of claim 17, further comprising using the recovered hydrogengas as a fuel.
 19. The method of claim 16, wherein the hydrocarbon fuelis selected from the group consisting of cyclohexane and benzene, ormixtures thereof.
 20. The method of claim 19, wherein the hydrocarbonfuel is cyclohexane.
 21. The method of claim 20, wherein the hydrocarbonfuel is benzene.
 22. The method of claim 16, wherein the hydrocarbonfuel and iodine are in a ratio of about 1:0.001 to about 1:2moles/moles.
 23. The method of claim 22, wherein the ratio is about1:0.01 to about 1:0.25 moles/moles.
 24. The method of claim 23, whereinthe ratio is about 1:0.05 to about 1:0.2 moles/moles.
 25. A fuel cellsystem comprising: a hydrogen gas generator of claim 16; and a fuel cellcapable of generating electricity by making use of hydrogen gas as afuel.
 26. The fuel cell of claim 25, wherein the hydrogen gas isgenerated by an increase in temperature and/or an increase in pressure.27. The fuel cell of claim 26, wherein the hydrogen gas is generated byan increase in temperature and an increase in pressure.
 28. The fuelcell of claim 26, wherein the hydrogen gas is generated by firstincreasing the temperature and then increasing the pressure.
 29. Thefuel cell of claim 26, wherein the hydrogen gas is generated by firstincreasing the pressure and then increasing the temperature.
 30. Thefuel cell of claim 26, wherein the temperature is increased to about 80°C. or higher.
 31. The fuel cell of claim 26, wherein the pressure isincreased to greater than about 2 atmospheres.
 32. The fuel cell ofclaim 26, wherein the temperature is between about 80° C. and 100° C.,and the pressure is between about 2 atmospheres and 2.5 atmospheres.